FYI, at docker-compose run -w /data/app app composer install I get
Creating drupal_app_run ... done
Running entrypoint.d script: /docker-entrypoint.d/blackfire.sh
Skipping Backfire: Set BLACKFIRE_ENABLED=yes to enable
Running entrypoint.d script: /docker-entrypoint.d/tuner.sh
Tuning: Apache: /var/run/tuner/apache2/tuner.conf
Tuning: PHP: /var/run/tuner/php/tuner.ini
Running entrypoint.d script: /docker-entrypoint.d/xdebug.sh
Skipping Xdebug: Set XDEBUG_ENABLED=yes to enable
Unable to locate a valid CA certificate file. You must set a valid 'cafile' option.
A valid CA certificate file is required for SSL/TLS protection.
You can disable this error, at your own risk, by setting the 'disable-tls' option to true.
[Composer\Downloader\TransportException]
The configured cafile was not valid or could not be read.
Arrived here via instructions at https://www.previousnext.com.au/blog/join-us-drupalgov-2020-code-sprint#set-up-a-development-environment--2 that use a gist that references
previousnext/php-apache:7.3-3.x-dev
FYI, at
docker-compose run -w /data/app app composer install
I get